General David Petraeus gestures during the Senate Intelligence Committee hearing on his nomination to be director of the Central Intelligence Agency in Washington, June 23, 2011. Petraeus has pleaded guilty in federal court to a charge of unauthorized removal and retention of classified information, the US Justice Department said on Tuesday.

Washington — President Nixon was furious. New York Times columnist Anthony Lewis was writing “sickeningly pro-communist” stories about the Vietnam War that needed to be countered, Nixon wrote in a May 19, 1972, memo to National Security Advisor Henry Kissinger.

Press leaks would be the administration’s retaliatory weapon. Mr. Nixon wanted Mr. Kissinger to get out the real story about the state of morale in North Vietnam – presumably bad.

“I do not want to hear any of those objections to the effect that this may compromise a source all that sort of thing … It is vitally important that … every possible leak or story which we can get out in this respect be gotten out,” Nixon wrote.

It’s rare to see such frank discussion at such a high level of Washington’s Game of Leaks. Nixon even named the underling Kissinger should use as the leaker: Army Gen. Al Haig, a future secretary of State.

But it’s a truth universally acknowledged that leaks, plants, and hybrid “pleaks” are common currency in national security and foreign affairs reporting. They’re used to preview possible strategies, sabotage bureaucratic rivals, and promote existing policy. Whistle-blowers use them to expose policies they believe to be mistaken.

Washington marinates in leaks. A Harvard survey in the mid-1980s found that 42 percent of senior government officials had thought it appropriate to leak to the press, at least once.

Leaking is newsworthy at the moment due to Gen. David Petraeus, the celebrated military leader and former CIA director who provided his classified journals, containing such sensitive information as the names of covert agents, to his lover and biographer, Paula Broadwell.

General Petraeus at first lied to the FBI when agents asked him whether he’d provided Ms. Broadwell this information. Eventually he pled guilty to one count of unauthorized removal and retention of classified information. He’ll almost certainly avoid prison time.

This has angered a lawyer for Stephen J. Kim, a former State Department contractor and arms expert who’s serving a 13-month sentence for disclosing classified information about North Korea to Fox News.

The disparity in punishments between Mr. Kim and Petraeus shows the long-standing double standard that holds when prosecuting leakers, attorney Abbe David Lowell wrote in a letter to Justice Department prosecutors.

Lower-level employees such as Kim are hit with Espionage Act cases because they lack the money and political connections to fight back, according to Mr. Lowell.

“High level officials … leak classified information to forward their own agendas (or to impress their mistresses) with virtual impunity,” wrote Lowell.

Given the historical record it’s hard to argue with that statement. But it’s also true that so much government information is classified that it’s very hard for government officials to have any kind of substantive discussion about tough subjects without disclosing secrets, purposefully or otherwise.

That makes leak cases a daunting moral and legal prospect for prosecutors as well.